1. Field of the Invention
This application relates to the field of speed responsive engaging devices such as clutches.
2. Prior Art
It has been known in the prior art that it is desirable to have a clutch to lock the impeller and turbine elements of a hydrodynamic device together to eliminate slippage therebetween under certain conditions to improve the efficiency of the device. It is further known that it is convenient to use the speed of rotation of an element as a signal to initiate engagement and disengagement of the clutch. The engagement is critical, for example, when the lock-up clutch is used in a hydrodynamic device in combination with an automatic transmission. During an automatic ratio change, it is desirable that the clutch be disengaged so that torque changes occurring during the shift will not be harsh, due to the hydrodynamic device absorbing shocks. If the clutch in the hydrodynamic device remains engaged during a shift, the shift control to provide smooth shifts is more exacting since the normal shock absorbing characteristic of the hydrodynamic device is eliminated.
As pointed out, it is known to utilize speed responsive clutches as lock-up clutches in a hydrodynamic device. Normally, to insure that such clutches are engaged at the proper time, expensive and complicated controls of the mechanical, electric, or hydraulic type are provided. Controls have been used to insure that the lock-up clutch is not engaged during an automatic shift. In addition, the clutch structures performing such functions are normally in themselves quite complicated.
In addition, lock-up clutches for a hydraulic torque converter as known in the prior art normally require modification of the torque converter structure to enlarge same to provide space for the lock-up clutch.
Accordingly, it is an object of the present invention to provide a clutch mechanism for a hydraulic torque converter which can be incorporated within the hydraulic torque converter with no requirement of increased axial or radial dimensions of the torque converter mechanism.
It is a further object of the present invention to provide a lock-up clutch which will engage and disengage at the proper time without the use of external control mechanisms to determine the points of engagement and disengagement. An additional object of the present invention is to provide a speed and torque responsive clutch in a hydrodynamic device which can be physically accommodated within the central toroidal space in the hydrodynamic device. Further, it is an important object of the present invention to provide a lock-up clutch for a hydrodynamic device which will automatically permit speed differentials within the device during specific operating conditions such as ratio change.